1. Field of the Invention
The present invention relates to a thermal head for a thermal recording machine, employed for a facsimile device, a printer and the like.
2. Description of the Prior Art
In a prior art thermal head for a thermal recording machine, a thermal accumulating layer is formed on a substrate, and thereon a plurality of thermal resistors are disposed in array in a direction corresponding to the scanning, where discrete electrodes electrically connect one end of the thermal resistors to a control element and a common electrode electrically connects the other end of the thermal resistors together; and a protection film is provided to prevent the thermal resistors and the discrete and common electrodes from abrasion, deterioration, etc.
Japanese Unexamined Patent Publication Nos. 181657/1986 and 181658/1986 disclose thermal heads where a substrate made of heat resistant resin, such as a glass epoxy substrate, is used, while a thermal accummulation layer is formed of a polyimide resin or a melamine resin; Japanese Unexamined Patent Publication No. 12357/1986 discloses a thermal head where a heat insulating layer is formed of a heat resistant resin such as a polyimide resin on the substrate surface; Japanese Unexamined Patent Publication No. 117760/1987 discloses a thermal head where a ceramic substrate is overlaid with a heat-insulating layer of polyimide resin and an inorganic material layer; Japanese Unexamined Patent Publication No. 189253/1988 discloses a thermal head where a thermal resistor is formed through a layer of heat resistant resin on a metal substrate, while a layer of inorganic insulating material is provided between the thermal resistor and the layer of heat resistant resin; Japanese Unexamined Patent Publication No. 164555/1987 discloses a thermal head where a thermal accumulating layer of polyimide resin is provided on a common electrode; and Japanese Unexamined Patent Publication No. 56566/1989 discloses a thermal head where a good conductor of heat is provided on the bottom portion of a thermal resistor.